Published on behalf of Sarah Graham
I have been busy preparing some beautiful manuscripts which are part of the Ingenious Impressions exhibition due to open on 27th February in the Hunterian Art Gallery. Special Collections conservation studio is an Aladdin’s Cave of materials and I wanted to see if it is possible to reproduce some of the illuminations using materials already in the studio or in my tool kit. In part 1 I look at the materials needed and in part 2 I try to recreate the illuminations.
Part 1: Preparing materials.
The focus of the exhibition is showing the change in technology from hand copied manuscripts to a system where multiple copies could be made at the same time. This transition was not instantaneous and there are some lovely examples of gilding on paper and printing on parchment. Illuminations on both parchment and paper are going to be displayed and so I will have a go at trying to show how both were produced. I should warn you though; I am neither an artist nor a scribe.
There are three variations of the gilding process that will be visible in the exhibition. They are shown in the photographs above (from left to right);
Raised gilding – where the shape of the design is built up using bole before applying the gold.
Flat gilding – where a binding substance (gum or size) is applied directly to the substrate (parchment or paper) to adhere the gold.
Flat gilding which has had a pattern pressed in after the application of gold leaf.
There are two illuminations which are quite similar, Sp Coll MS Hunter 282 and Sp Coll Hunterian By.2.3. They also provided an interesting comparison as the first is raised gilding on parchment and By.2.3 is flat gilding on paper. As well as using the same initial, they also have a similar design of intertwining foliage, The gaps in these are filled (in both instances) with red, blue and green.
Up on top of the storage shelves were some really fine examples of parchment made from goat (left), calf (right) and sheep. These, however, are too good to experiment with. I humidified and uncurled the end of another sheet which should work well as a support. For the paper, there is a handmade laid paper that is a similar colour and weight to the 15th century example that is regularly used in bookbinding.
Another important material is the gold. Fortunately there is a cupboard in the studio with a couple of books of gold leaf.
Making medieval bole
Size or bole is normally used to adhere gold to the parchment or paper support. Hopefully rabbit skin glue will work as a traditional size for the flat gilding although making the adhesive from boiled parchment was scraps was more traditional. Both animal glues are responsive to heat so should reactivate when breathed on.
The raised gilding is not very high because it lives between leaves of a closed book but the bole causes the gold to sit slightly proud of the parchment. This is caused by a more viscous adhesive, gesso coloured with Armenian bole. There are two different 15th century recipes for bole. One comes from Cennini’s Il Libro dell’ Arte translated from Italian in 1933 and the Göttinger Model book which has been translated and digitised as part of Project Gutenberg.
The ingredients for both recipes are very similar however Cennini describes a process of slacking plaster of Paris by mixing with water for about a month, rather than using chalk. Thankfully, advice from a blog discussing Jerry Tresser’s research into gesso in Cennini’s recipe said that the chemical properties of plaster of Paris change instantaneously when water is added causing the mixture to dry rather than set. It works and a months work is reduced to 5 minutes of stirring. This quick setting material can then be used as an inert bulking material in the bole.
The author of the Model book (fol.4r) is even kind enough to give us quantities.
Ground chalk (size of a small tree nut)
egg white (whisked and left out overnight),
armenian bole (size of a small hazelnut)
half a hazelnuts worth of sugar
half a pea of cinnabar.
For the bole to function properly, it needs to be; fluid enough to create the gold design, hygroscopic (sensitive to water), flexible so it won’t crack and most importantly, have enough adhesive strength to bond the gold to the support. We don’t have any cinnabar but I think it is a mercury derivative so it is probably best to give it a miss.
I mixed the ingredients together trying to get rid of any lumps with my makeshift glass muller and slab. They were then tested on an offcut of paper and to my surprise the gold bonded to the bole and was able to be burnished.
Now I just have to hope it will work on the parchment!
Categories: Special Collections